1984 300D, mostly stock

Battery is 3 years old, MBZ. Alternator is 5 months old, 3rd replacement (several reman defects in a row) in less than a year. 65 AMP Bosch.

At idle my DMM reads 14V. With headlights with highbeams on, heater on full, radio on, rear defroster on, and brake pedal depressed, I still get 12.75 V. Raised idle brings it back up to around 13.5V.

I haven't load tested the battery, and it may be part of the issue. Glows and starts without hesitation every morning (daily driver). But I've noticed my driver's headlight is rather dim (stock, Bosch sealed beams). If I hit the high beams the driver's headlight goes out completely. Additionally, sometimes after a long cold night, after driving for a few minutes, hitting the brakes will shut the radio off and dim the headlights/dashlights quite a bit. Seems to act like there's not enough power in the system, but will shut off and start up no problem.

Any clue as to where to start (after load testing the battery)?

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

First thing that jumped out to me is you have a ground problem.
Check all your ground points, Battery, Ground Cable at the Adaptor Plate at rear of engine.
Under the Hood there is a couple of Grounds behind the head lights I believe on the inner fenders

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works